Puffed-up Edges of Planet-opened Gaps in Protoplanetary Disks. I. Hydrodynamic Simulations

Dust gaps and rings appear ubiquitous in bright protoplanetary disks. Disk-planet interaction with dust trapping at the edges of planet-induced gaps is one plausible explanation. However, the sharpness of some observed dust rings indicate that sub-millimeter-sized dust grains have settled to a thin layer in some systems. We test whether or not such dust around gas gaps opened by planets can remain settled by performing three-dimensional, dust-plus-gas simulations of protoplanetary disks with an embedded planet. We find planets massive enough to open gas gaps stir small, sub-millimeter-sized dust grains to high disk elevations at the gap edges, where the dust scale height can reach similar to 70% of the gas scale height. We attribute this dust puff up to the planet-induced meridional gas flows previously identified by Fung & Chiang and others. We thus emphasize the importance of explicit 3D simulations to obtain the vertical distribution of sub-millimeter-sized grains around gas gaps opened by massive planets. We caution that the gas-gap-opening planet interpretation of well-defined dust rings is only self-consistent with large grains exceeding millimeter size.

Automated summary

Dust gaps and rings are commonly found in bright protoplanetary disks, with some sharp dust rings indicating settlement of sub-millimeter-sized dust grains. Planets massive enough to open gas gaps can stir small dust grains to high disk elevations, attributed to meridional gas flows induced by the planet. Three-dimensional simulations are crucial for obtaining the vertical distribution of sub-millimeter-sized grains around gas gaps opened by massive planets.